The invention relates to sound-absorbing acoustic covers, and more particularly, to cover elements for use as a component in a gap-free acoustic cover comprised of a perforated plate covered on a side facing an enclosed space with a layer of nonwoven fiber material covering perforations of the plate, and a sound-inhibiting layer lining the side of the plate facing away from the enclosed space.
Known structural configurations for sound-absorption are used particularly for acoustic covers suspended under the ceilings of rooms. The sound waves pass from the room through the sound-permeable layer of plaster or the like, and into the perforations of the perforated plate, and are sharply attenuated in the sound-inhibiting layer disposed behind said plate. An acoustic cover comprised of such cover elements has outstanding acoustic properties.
It has been found in practice however, that such covers act as a type of dirt filter. When heated air circulates through the cover, or forced air in air conditioned rooms, dirt particles carried along in the circulating air are concentrated in the region of the perforations and are filtered out by the plaster layer. This causes a noticeable and unattractive soiling of the loci of the plaster layer which are located in front of and which cover the perforations.
This effect is accentuated if installation workers take shortcuts and fail to apply the inhibiting layer immediately behind the perforated plate, which requires cutting the inhibiting layer to size, due to the presence of the supporting profile members which are spaced at regular intervals. The workers may elect to merely apply the inhibiting layer over the base profile members instead of in the rectangular spaces between them, so that a substantial void space exists between the perforated plate and the inhibiting layer, thereby facilitating air circulation and accelerating the soiling of the plaster layers.